The present invention relates to an actuation system for a vehicle passenger protective device which detects a collision state of a motor vehicle to actuate a passenger protective device (safety device) such as an airbag in accordance with the detection result.
A conventional actuation system is known and disclosed as "Airbag Actuation Control System" in the Japanese Patent Publication No. 59-8574 wherein an acceleration sensor is provided to detect an acceleration of a motor vehicle at the time of collision of the motor vehicle to generate a signal indicative of the vehicle acceleration. The acceleration signal is integrated for a predetermined integration period so that an airbag is actuated when the integration value exceeds an actuation predictable level. In addition, in the system the integration period is automatically lengthened when the integration value exceeds the actuation predictable level within the integration period, thereby accurately catching the generation of the acceleration signal in relation to the collision to improve the collision decision accuracy.
There is a problem which arises with such a system, in that, since the integration period is lengthened when the acceleration signal exceeds an actuation predictable level irrespective of the timing of the generation of the acceleration signal for the integration period, then if the integration value of the acceleration signal generated when the motor vehicle is running on an irregular road (for example) exceeds the actuation predictable level, the integration period is further lengthened to thereby obtain excess information from the integration result, whereby it is impossible to accurately decide the collision of the motor vehicle.
In addition, there is the possibility that the acceleration signal includes a drift component due to causes, such as, the passage of time and the variation of the temperature. Hence, if the acceleration signal from the acceleration sensor is directly integrated, it becomes difficult to accurately decide the collision of the motor vehicle.